Angelita Gambuti

Evolution of Phenolic Compounds and Astringency during Aging of Red Wine: Effect of Oxygen Exposure before and after Bottling

The aim of this study was to evaluate the effect of oxygen exposure of red wine, before (micro-oxygenation) and after (nano-oxygenation) bottling, on the phenolic composition and astringency of wine. The astringency was evaluated by sensory analysis and by a method based on the SDS-PAGE of salivary proteins after reaction of saliva with wine (SPI, saliva precipitation index). Micro-oxygenation caused a stabilization of color, but this effect disappeared after long aging. For the wine with the lower pH a decrease of wine astringency and SPI was observed 42 months after micro-oxygenation. Oxygen ingress through the closure postbottling was positively correlated with the decrease of SPI. Therefore, the astringency and reactivity of wines toward salivary proteins of a bottled red wine can be modulated by controlled oxygen exposure during aging. For both experiments the effect of oxygen exposure depended on wine composition.

Application of the SPI (Saliva Precipitation Index) to the evaluation of red wine astringency

The aim of this work was to evaluate the astringency of red wines by means of a SDS-PAGE based-method. The optimization of the in vitro assay, named SPI (Saliva Precipitation Index) that measured the reactivity of salivary proteins towards wine polyphenols, has been performed. Improvements included the choice of saliva:wine ratio, saliva typology (resting or stimulated saliva), and temperature of binding. The LOD (0.05 g/L of condensed tannin) and LOQ (0.1g/L of condensed tannin) for the binding reaction between salivary proteins and tannins added in white wine were also determined. Fifty-seven red wines were analysed by the optimised SPI, the Folin-Ciocalteu Index, the gelatine index, the content of total tannins and the sensory quantitative evaluation of astringency. A significant correlation between the SPI and the astringency of red wines was found (R(2)=0.969), thus indicating that this assay may be useful as estimator of astringency.

Biochemical features of native red wines and genetic diversity of the corresponding grape varieties from Campania region.

Campania region has always been considered one of the most appreciated Italian districts for wine production. Wine distinctiveness arises from their native grapevines. To better define the chemical profile of Campania autochthonous red grape varieties, we analysed the phenolic composition of Aglianico di Taurasi, Aglianico del Vulture, Aglianico del Taburno, Piedirosso wines, and a minor native variety, Lingua di Femmina in comparison with Merlot and Cabernet Sauvignon, as reference cultivars. A genetic profiling was also carried out using microsatellite molecular markers with high polymorphic and unambiguous profiles. Principal component analysis applied to 72 wines based on the 18 biochemical parameters, explained 77.6% of the total variance and highlighted important biological entities providing insightful patterns. Moreover, comparison of SSR-based data with phenylpropanoid molecules exhibited a statistically significant correlation. Our approach might be reasonably adopted for future characterisations and traceability of grapevines and corresponding wines.

Sulfur Dioxide and Glutathione Alter the Outcome of Microoxygenation

Cabernet Sauvignon wines with low and high levels of SO2 and glutathione (GSH) were treated with microoxygenation (MOx) in a 23 L pilot experiment. Treatment generally increased O2, aldehydes, and derived products while decreasing anthocyanins, vanillin reactive flavonoids, and SO2. During the treatment, when free SO2 was depleted in the low GSH wine, dissolved oxygen levels collapsed, with a concomitant increase of acetaldehyde, pyranoanthocyanins, polymeric pigments, and acetaldehyde acetals. This outcome indicates a possible acceleration of the Fenton oxidation of ethanol and other oxidation reactions by way of direct free radical reactions with oxygen. In wines containing high levels of GSH, anthocyanins were protected, revealing a protective effect for GSH for the first time. However, the protection was only partial, and while GSH may be effective in preventing the loss of volatile thiols, its use does not prevent color stabilization in red wines. Because both SO2 and GSH are able to modulate the reactions initiated by MOx, but have somewhat dissimilar reactions, it may be possible to manage oxidation outcomes by choosing one or the other during wine processing and aging. Because SO2 and O2 levels are related to large differences in MOx reaction rates, those levels are candidate indicators of the rate of MOx oxidation. Alternatively, the levels of acetaldehyde acetals may be useful indicators of the cumulative extent of oxidation under MOx conditions.

Earthy off-flavour in wine: evaluation of remedial treatments for geosmin contamination.

Seven treatments (activated charcoal, bentonite, PVPP, yeast cell walls, potassium caseinate, zeolite and grape seed oil) were evaluated for their efficacy in decreasing the concentration of geosmin, responsible for earthy off-flavour in wine. In the red wine the potassium caseinate and grape seed oil treatments decreased the concentration of geosmin by 14% and 83%, respectively, while in the white wine, the activated charcoal and the grape seed oil were able to decrease the concentration of geosmin by 23% and 81%, respectively. The effective treatments in decreasing geosmin also decreased aroma volatile compounds, most of all esters, responsible for fruity notes. Considering the OAVs (concentration/odour threshold) only the treatment with grape seed oil was able to decrease the relative contribution of geosmin to the profile of the odour active compounds, both in red and in white wine. Sensory analysis confirmed the efficacy of the grape seed oil as a remedial treatment.

Alcohol reduction in red wines by technological and microbiological approaches: a comparative study

Background and Aims The aim of this work was to assess and compare the chemical composition and colour characteristics of Barbera red wines obtained after partial alcohol reduction using three promising methodologies for implementation at the industrial level. Methods and Results Alcohol reduction was achieved by: (i) pre-fermentation addition of liquid derived from grape must (reverse osmosis by-product); (ii) mixed fermentations with strains of Starmerella bacillaris and Saccharomyces cerevisiae; and (iii) dealcoholisation of wine post-fermentation with a polypropylene membrane. The microbiological approach enabled the production of wines with a slightly lower alcohol concentration (−0.2 to −0.3% v/v), while facilitating the release of anthocyanin and some esters of fatty acids (ethyl hexanoate and ethyl dodecanoate) that could contribute positively to wine aroma with pleasant nuances. The low impact of the partial replacement of grape juice on the chemical composition and chromatic characteristics of Barbera wines makes this technique a good option for reducing the ethanol concentration by up to 1.0–2.0% v/v. In contrast, the use of a polypropylene membrane influenced negatively the composition of red wines by reducing significantly the concentration of esters (−60%) and anthocyanin (−17%), independently of the dealcoholisation level (up to −2% v/v). Conclusions The alcohol reduction strategies can greatly influence the volatile and phenolic composition of the wine. The choice of either a technological or microbiological approach in the wine industry is dependent on the alcohol reduction required. Significance of the Study This is the first comparative study of three strategies to reduce the alcohol concentration on the same batch of must/wine.

Chip electrophoresis as a novel approach to measure the polyphenols reactivity toward human saliva

Saliva is a biological fluid with a multifunctional role that makes it interesting in terms of research and diagnostic possibilities. In food research, human saliva represented a useful tool by which we measure the tactile sensation elicited by polyphenol‐rich beverages called astringency. A method based on SDS‐PAGE analysis of saliva before and after the binding reaction with wine polyphenols has been successfully used in previous studies for measuring wine astringency by means of the saliva precipitation index. In this work, chip electrophoresis was used alternatively to SDS‐PAGE and results were compared. Chip electrophoresis provides a very good reproducibility for wine and grape astringency. Moreover, this approach is much faster than the conventional SDS‐PAGE method requiring several hours for an analysis. Another advantage over traditional gel is lower sample and reagent volume requirements, as well as the lower and less toxic wastes, contributing benefits to health and environment. The application of this novel method allowed, using the principal component analysis, to distinguish grapes and wines according to the saliva precipitation index and structural characteristics determined by the phoroglucinolysis analysis.

Treatment by fining agents of red wine affected by phenolic off-odour

Although phenolic off-odour is very detrimental for red wine quality, there is a lack of easy-to-use methods able to decrease the levels of the responsible compounds 4-ethylphenol (4-EP) and 4-ethylguaiacol (4-EG) and to improve the sensory quality of the contaminated wines. To this aim, an alternative use of fining agents (activated charcoal, PVPP and zeolite) was evaluated. Two levels of ethylphenol contamination were considered: a naturally low contaminated red wine and the same wine spiked with 4-EP and 4-EG. The impact of the treatments on desirable aroma volatiles, polyphenols and colour was also evaluated. The effectiveness in diminishing the intensity of the phenolic off-odour was assessed by descriptive sensory analysis. The activated charcoal and PVPP significantly decreased the concentrations of 4-ethylguaiacol and 4-ethylphenol in the naturally contaminated wine, while none of the tested fining agent was effective in the spiked one. Polyphenols and colour were slightly affected, to the same extent for the two treatments. Charcoal and PVPP additions negatively impacted the concentration of the aroma volatiles, especially esters, with the activated charcoal achieving a higher decrease. The sensory outcome of both treatments was the decrease in the intensity of phenolic off-odour, with charcoal achieving a higher decrease. Interestingly, in spite of the decrease in esters, also a significant increase in the intensity of “red fruit” odour occurred.

Performance of a protein extracted from potatoes for fining of white musts

In this study, the potentiality of Patatin (P), a protein extracted from potato, as must fining agent was investigated on musts obtained from two South Italy grape cultivars (Falanghina and Greco). Besides P, fining agents as bentonite (B) and potassium caseinate (C) were assayed at different concentrations. The rate of sedimentation, the decline of turbidity during time, the absorbance at 420 nm, the GRP (grape reaction products) and hydroxycinnamic acids (HCA) concentrations were determined. The comparative trials showed that P is a suitable fining agent to prevent browning and decrease haze during must settling because its effect on grape phenolics, brown pigments and turbidity is comparable and/or better than that detected for C. Its use as single fining agent or in combination with B depends on must characteristics.

An extract procedure for studying the free and glycosilated aroma compounds in grapes

In this study seven published methods of extraction of skin free and bound volatile compounds have been compared. The free and bound volatiles were separated by solid phase extraction (SPE) and then analysed by gas chromatography coupled with mass spectrometry (GC-MS). The results showed that the extraction of volatile compounds from grapes is highly affected by extraction solution features. The solution at pH 3.2 and 0% ethanol resulted the most effective as it led to the extraction of a higher number and amount of free and glycosilated volatile compounds. The selected extraction method of grape skin and the process of pulp juice were validated for quantitative determination of a wide range of grape aroma compounds. A total of 37 free and bound grape aroma compounds were quantified by GC-MS in selective ion monitoring modality (SIM). Among them, 26 volatile compounds resulted validated in grape skin and pulp juice.